Current bi-optic bar code scanner designs produce patterns arranged to read labels passed by the scanner. The patterns are such that action of an operator swiping a bar code across the scanner window will move a typical label of nominal truncation across several scan lines allowing the label to be read. However, with truncated or otherwise difficult bar code labels operators often present the label to the scanner window instead of swiping them. As there are a limited number of spatially separate scan lines it is possible for the label to miss them all and not be read. For example, if a label is presented adjacent a fan of scan lines, but not over the fan of scan lines, then the bar code will not be read.
Commonly assigned U.S. Pat. Nos. 5,229,588, 5,684,289, and 5,886,336 disclose a typical dual aperture optical scanner. The scanning light beams from a laser diode pass through substantially horizontal and vertical apertures to provide more item coverage than a single aperture scanner.
In an effort to increase item coverage, optics designers are increasing the number of scan lines, line length, and scan angles by increasing the number of lasers and pattern mirrors in the scanner. The addition of these components consequently increases cost.
Alternative approaches have been considered in which the scan lines are moved orthogonally to the direction of the lines. This has been achieved by the movement of the laser light source, within the scanner, or the movement of the output mirror. Both of these are mechanically complex solutions which are not suitable for multi-laser or large bi-optic scanners.
As will be illustrated in more detail below, with reference to FIGS. 1 to 6, present day scanners comprise, a laser assembly, spinner assembly, collection optics, pattern mirrors, detector assembly, electronics, a window and scanner housing which contains all the individual assemblies. In operation, the laser beam intercepts the polygon spinner rotating about a single axis and is subsequently scanned in a single plane towards a set of pattern mirrors which reflect the individual scan lines out the window and onto a barcode. The laser energy is then reflected off of the barcode and a portion is gathered by the collection optics and focused onto the detector generating a signal to be decoded by the electronics. The positions at which the scan lines exit the window are static, and are contained in a relatively small portion of the hemispherical volume available outside and adjacent to the window (FIG. 6).